Installer cannot use existent file system as root
Binary package hint: ubiquity
I wanted to keep my ext3 file system with gigs of photos and other stuff. So I deleted everything of the old Ubuntu expect of my data.
But the installer of Gutsy refused installing on that partition. I had to make the file system smaller with gparted, build a new partition, install Ubuntu on that, move the data on the new partition, delete the old one and resize the new to full size. That sucks!